The aperture is made up of mechanical blades that increases or decreases in size depending on the aperture you select.

In humans, the iris is a thin, circular structure in the eye, responsible for controlling the diameter and size of the pupil and thus the amount of light reaching the retina.

How Does Aperture Affect Exposure?

"Exposure - how bright or dark your image is."

As mentioned previously, you can increase or decrease the amount of light that passes through to your camera based on the size of the lens aperture.

This can have a direct affect on your exposure if the aperture is too large or too small. That is if all else is equal, and you’re not adjusting your ISO and/or Shutter Speed. Let’s keep it simple and focus on the lens aperture for now.

For example, if too much light passes through the lens, you end up with an overexposed image. And, if not enough light gets to the camera sensor,

your image will be underexposed.

A perfect (or balanced) exposure is when the image is rich in details in both the highlights and shadows.

If you overexpose the image, you’ll lose details in the highlights. The opposite happens with an underexposed image. All the details in the shadows are lost.

The goal should be to capture a proper, balanced exposure in-camera. If not, you’ll end up with a lower quality image that you’ll have to try and fix in Photoshop (or Lightroom).

For example, if the details have been clipped at the time of capture, you can’t get them back.

Here are the results of only changing the aperture (each image shot with ISO 200 | 1/60th):

An aperture of f/1.8 allowed too much light to be captured and results in an overexposed image.

An aperture of f/2.8 allows the proper amount of light to be captured for a well-balanced exposure.

An aperture of f/4 doesn’t allow enough light to be captured and results in an underexposed image.

NOTE:

There are a few factors that will determine if your details are clipped in addition to how much light enters via the aperture in the lens:

The dynamic range of your camera

Whether you’re shooting in JPEG or RAW

Shutter Speed

ISO

Your Aperture Choice Affects Your Photos Creatively

The aperture isolates the world you see and gives you the ability to craft your photos based on your creative vision.

Chris Parker

Before you select your aperture camera setting, you may want to consider the creative outcome. This will help you decide which aperture settings might be best for the final image.

For example:

Do you want to blur out the background or keep it sharp?

What about the foreground?

Do you want your subject to be in focus or selectively in-focus?

You can harness the available light by adjusting

the size of the aperture.

Before the light, from your scene, reaches your camera’s sensor, you can manipulate that light based on your creative vision. In a way, you’re painting with light.

Think of how a painter uses different size brushes to create a masterpiece on canvas.

Your canvas is your camera’s sensor, and your paint is light. You can control how much light to paint with by changing the size of the aperture.

Plus, the different sizes of your aperture also gives you creative options for your final masterpiece.

There are specific aperture sizes that can be used to blur part of your image. And still, others that can enhance the sharpness of your photo.

We’ll explore these different lens apertures in more detail, with some real-world examples, later on in this aperture guide.

A large aperture was used to creatively blur out the background.

A small aperture was used to keep both the foreground and background in focus.

My creative vision for this shot was to keep a portion of the foreground in focus. What type of aperture did I use for this shot, small or large?

What is BOKEH, and How Can You Use It Creatively?

Bokeh "A photography term used to describe the characteristics of how the background looks when blurred out. Bokeh appears as little circles in the out of focus areas."

Bokeh occurs when a light source is blurred out due to the length of your lens, the distance the subject (s) are to the lens and the aperture.

However, you can selectively choose a large aperture to enhance this effect with a shallow depth of field.

In this image, a macro lens was used with a large aperture. Due to the lights being very far from the lens, the Bokeh effect was created.

Also, the shape of the Bokeh can be round or the shape of the aperture itself.

What Is Depth of Field (To Aperture)?

Depth-of-Field (DOF)

"The distance between the foreground and background that appears acceptably in focus.

A shallow DOF refers to a smaller area of the image in focus. A large depth of field refers to more of the foreground and background in focus.

Depending on the lens, aperture selected, and the distance to the main subject can affect how much of the scene is in sharp focus."

Depth of field is a term used to describe how much of the scene is in focus or out of focus. This term is sometimes referred to as DOF.

The point at which you focus on is the starting point of the depth of field.

That focus point will be the sharpest part of the entire image.

Depending on the aperture used, parts of the image will become less and less in-focus.

This goes for both the foreground and background.

The focal length of your lens and the distance of the subject to the lens can also affect the depth of field (and Bokeh).

For example, a longer lens can achieve a similar depth of field compared to a large aperture.

If a background is very blurry, compared to the foreground, it’s known to have a “shallow” depth of field.

A larger depth of field is when both the foreground and background are sharp.

In the following image, the subject is completely in focus, and the background is blurred out.